15 y old guy and 11 y old girl?

This is about a hypothetical, completely nonual, consensual relationship. My cousins friend has a huge crush on me for a long time and she's really is kinda pretty. Now, I don't have a gf right now but I could have at least 2 in one second. Anyway, I'm not looking for any ual relationship cuz I'm a good catholic so I'm waiting till Im married or I found the right girl. Anyway, common sense tells me to wait till she's atleast 16-17 but what could be so bad? Shes going to JHS next year and I'm I'm HS so I'm guessing she's getting a phone or aim sn soon so I'll be able to talk to her a lit more because as of now I only rarely see her when I sleep over my cousins house. Anyway, opinions?